Endogenous superoxide is a key effector of the oxygen sensitivity of a model obligate anaerobe
| Autor: | Zheng Lu, Ramakrishnan Sethu, James A. Imlay |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
0301 basic medicine
030106 microbiology medicine.disease_cause Superoxide dismutase 03 medical and health sciences chemistry.chemical_compound Bacterial Proteins Superoxides Escherichia coli medicine Anaerobiosis chemistry.chemical_classification Reactive oxygen species Multidisciplinary biology Superoxide Obligate anaerobe equipment and supplies Oxygen Bacteroides thetaiotaomicron Oxidative Stress Enzyme PNAS Plus chemistry Biochemistry Fumarase biology.protein bacteria |
| Zdroj: | Proceedings of the National Academy of Sciences. 115 |
| ISSN: | 1091-6490 0027-8424 |
| DOI: | 10.1073/pnas.1800120115 |
| Popis: | It has been unclear whether superoxide and/or hydrogen peroxide play important roles in the phenomenon of obligate anaerobiosis. This question was explored using Bacteroides thetaiotaomicron, a major fermentative bacterium in the human gastrointestinal tract. Aeration inactivated two enzyme families-[4Fe-4S] dehydratases and nonredox mononuclear iron enzymes-whose homologs, in contrast, remain active in aerobic Escherichia coli Inactivation-rate measurements of one such enzyme, B. thetaiotaomicron fumarase, showed that it is no more intrinsically sensitive to oxidants than is an E. coli fumarase. Indeed, when the E. coli enzymes were expressed in B. thetaiotaomicron, they no longer could tolerate aeration; conversely, the B. thetaiotaomicron enzymes maintained full activity when expressed in aerobic E. coli Thus, the aerobic inactivation of the B. thetaiotaomicron enzymes is a feature of their intracellular environment rather than of the enzymes themselves. B. thetaiotaomicron possesses superoxide dismutase and peroxidases, and it can repair damaged enzymes. However, measurements confirmed that the rate of reactive oxygen species production inside aerated B. thetaiotaomicron is far higher than in E. coli Analysis of the damaged enzymes recovered from aerated B. thetaiotaomicron suggested that they had been inactivated by superoxide rather than by hydrogen peroxide. Accordingly, overproduction of superoxide dismutase substantially protected the enzymes from aeration. We conclude that when this anaerobe encounters oxygen, its internal superoxide levels rise high enough to inactivate key catabolic and biosynthetic enzymes. Superoxide thus comprises a major element of the oxygen sensitivity of this anaerobe. The extent to which molecular oxygen exerts additional direct effects remains to be determined. |
| Databáze: | OpenAIRE |
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